This is the cumulative outbound byte counter for the pseudowire's entire tracked lifetime since the last discontinuity, complementing cpwVcPerfTotalOutHCPackets to give total data volume rather than just packet counts. It's the figure most directly useful for billing a customer on a metered pseudowire service, since it represents actual bytes carried rather than an interval snapshot that could miss traffic bursts between polls. If this counter and cpwVcPerfTotalDiscontinuityTime both reset unexpectedly at the same moment, that's strong evidence the line card or router carrying the VC reloaded.